This book provides a comprehensive, systematic description of modern timekeeping and its specializations. Introductory chapters discuss the concept of time and its definition, then briefly look at pre-Atomic Era timekeeping to set the stage for the introduction of the atomic clock. Subsequent chapters focus on concepts such as frequency stability and measurement uncertainty, as well as computer network time-synchronization protocols including Network Time Protocol (NTP) and Precise Time Protocol (PTP). The book then delves into the nuts and bolts of the Global Navigation Satellite Systems (GNSS), Two-Way Satellite Time and Frequency Transfer, and Optical Time and Frequency Transfer. Timescale theory is then described as a way to combine clock data, and the algorithms and procedures used to generate Coordinated Universal Time (UTC) are given. Finally, there is a look at modern applications of timekeeping and time transfer.
Featuring a glossary of all key terms, this book is highly recommended for trained or incoming physicists, engineers, or mathematicians working, for example, in manufacturing or timing laboratories. Additionally, it is suitable for use in introductory university courses dealing with the subject of timekeeping.

About the Author: Dr. Parameswar Banerjee received his undergraduate degree from the University of Calcutta and his Ph.D from the University of Burdwan. He joined National Physical Laboratory, India (NPLI) in 1976, where for thirty five years he worked on circuit design, satellite communication, time measurement, GNSS time transfer, and timescales. The patents he secured for designing NPLI's digital telephone service have been licensed to four different manufacturers. He served as Acting Director of NPLI for a few months, and in 2008 he became head of the Electrical and Electronics Standards Division.

After retirement he became a professor at Amity University and a visiting researcher at Burdwan University, supervising many undergraduate and PhD students while also developing curricula and chairing academic committees.

He is a Senior Member of Institute of Electrical and Electronics Engineers (IEEE) and a Fellow of the Institution of Electronics and Telecommunication Engineers (IETE), the Metrology Society of India (MSI), the International Union of Radio Science (URSI), and the Institution of Engineering and Technology (IET).

He has published more than 100 papers, given more than 60 invited talks, presented 90 conference papers, and holds 7 patents. He has received the Union of Radio Scientists (URSI) Young Scientist Award, the 2006 IETE Hari Ramji Toshniwal Gold Medal, and the Lifetime Achievement Award from the SKF Group of Institutes.

Dr. Demetrios Matsakis grew up in St. Louis, received a BS in physics from MIT, and a PhD in physics from UC Berkeley, where he studied under Nobel Laureate Charles Townes. He then worked for 40 years at the U.S. Naval Observatory (USNO), where he at first used radio interferometry and built water-vapor radiometers to measure the variable rotation of the Earth. In 1989 he was asked to work part-time on a mercury stored-ion clock. In 1997 he became director of the USNO's Time Service department, and 16 years later he became Chief Scientist.

Now a consultant, he has worked on the faculty of Virginia Tech on finding better methods to predict the Earth's rotation, and on Kalman filter theory. As Chief Scientist for Masterclock he advises on and tests new products, writes a blog, and otherwise remains active in the timekeeping community. Frequently asked to review articles for technical journals, he is also a special editor for the GPS Solutions topical collection on timekeeping.

He has participated in or chaired numerous national and international committees and working groups, served for three years as president of the International Astronomical Union's Time Commission (#31), and represented the USA in Paris and Geneva. He has published over 160 scientific papers covering most aspects of timekeeping including Earth rotation, timescales, pulsars, and time-transfer. He holds one patent and published five science fiction short stories. In 1996 he received the USNO's Newcomb award, the highest internal award for science research, and in 2023 he was given the Institute of Navigation's PTTI Distinguished Service Award.